1. Technical Field
The present invention relates to composite substrates and, in particular, to composite substrates with predetermined porosities that may be utilized, for example, within a porosity reference standard or during evaluation of defects in gas turbine engine components.
2. Background Information
Non-destructive investigation “NDI” may be performed on organic matrix composite components to inspect for defects such as delaminations and/or relatively high porosities (e.g., typically greater than 2%). The term “porosity” describes a ratio of a volume of pores or voids within a composite component to a volume of composite component material. Non-destructive investigation may be performed using non-destructive investigation “NDI” machines such as, for example, ultrasound machines and thermography machines.
NDI machines are typically calibrated utilizing a porosity reference standard that includes a plurality of test panels, each having a different porosity level and depth within the panel. A typical test panel may include a polytetrafluoroethylene or plastic inclusion that is inserted within a composite test panel body. The inclusion is designed to replicate a certain porosity level when the test panel is inspected by an NDI machine. Alternatively, a composite test panel body may include a plurality of drilled apertures that are similarly designed to replicate a certain porosity level when the test panel is inspected by an NDI machine. Such test panels, however, may be difficult to implement in practice, which may lead to delays in delivering high cost organic matrix composite components to customers.